Epoxy compounds have a wide field of application in the production of plastics, polymer foams, surface coatings, and coating materials. It is desirable for these substances to have a very high epoxy oxygen content, and at the same time the volatile component content must be as low as possible in order to prevent exudation (fogging) on the plastics parts. Finally, the products must be sufficiently heat-stable; i.e., at relatively high temperatures as encountered during the preparation of the polymers, there must be no unwanted crosslinking of the epoxides with one another and no increase in viscosity.
From the prior art it is known to subject epoxy compounds prepared by the performic acid process to neutral washing by repeated treatment with water or aqueous alkali and to remove catalyst residues together with the washing water. Normally, this is followed by the phases being separated, the washing water being stripped off or removed by centrifugation, and the residual moisture content in the product being removed by adding sodium sulfate or by vacuum drying. Alternatively, traces of acid can be removed from the epoxides by introducing gaseous ammonia, by neutralization with anhydrous sodium carbonate, by azeotropic distillation, or by the use of anion exchangers [cf. Chem. Ztg. 95, 684(1971)].
Although the measures of the prior art, and especially the known method of wet refining with alkali metal hydroxide solution, make it possible to reduce the number of washing steps, it is nevertheless the case that under these conditions, from epoxidized esters, for example, surface-active soaps having emulsifying properties may be formed, and phase separation is therefore retarded. At the same time, there is increased incidence of epoxy ring opening reactions, which reduce the epoxy oxygen content.
The object of the invention was therefore to provide a process for preparing heat-stable epoxides which is free from the disadvantages depicted.